diff --git a/examples/first/first.c b/examples/first/first.c
index 9e6b247..30d7171 100644
--- a/examples/first/first.c
+++ b/examples/first/first.c
@@ -7,9 +7,9 @@ int main(void)
   card_os_put_rect((card_os_rect){ 0, 0, 0, 0, 0, 240, 320 });
 
   card_os_put_rect((card_os_rect){
-    .r = 0xFF, .g = 0xFF, .b = 0xFF, .x = 60, .y = 80, .w = 120, .h = 160 });
+    .r = 0xFF, .g = 0xFF, .b = 0xFF, .x = 60, .y = 80, .w = 160, .h = 160 });
 
-  while (value < 250)
+  while (!card_os_get_button(OS_BUTTON_MIDDLE))
   {
     card_os_put_rect((card_os_rect){
       .r = value++, .g = 0, .b = 0, .x = 0, .y = 0, .w = 60, .h = 60 });
diff --git a/include/user/card-os.h b/include/user/card-os.h
index 267fcb7..842e39f 100644
--- a/include/user/card-os.h
+++ b/include/user/card-os.h
@@ -6,7 +6,8 @@
 typedef enum
 {
   OS_CMD_SBRK,
-  OS_CMD_DRAW_RECT
+  OS_CMD_DRAW_RECT,
+  OS_CMD_GET_BUTTON
 } os_command;
 
 typedef struct
@@ -23,6 +24,14 @@ typedef struct
   uint16_t x, y, w, h;
 } card_os_rect;
 
+typedef enum
+{
+  OS_BUTTON_LEFT,
+  OS_BUTTON_MIDDLE,
+  OS_BUTTON_RIGHT
+} card_os_button;
+
 void card_os_put_rect(card_os_rect rect);
+int card_os_get_button(card_os_button button);
 
 #endif // CARD_OS_USER
diff --git a/src/card-os-user.c b/src/card-os-user.c
index d2b95a7..b236d7d 100644
--- a/src/card-os-user.c
+++ b/src/card-os-user.c
@@ -27,6 +27,13 @@ void card_os_put_rect(card_os_rect rect)
   oscall(&(os_message){ .command = OS_CMD_DRAW_RECT, .data = &rect });
 }
 
+int card_os_get_button(card_os_button button)
+{
+  int status = button;
+  oscall(&(os_message){ .command = OS_CMD_GET_BUTTON, .data = &status });
+  return status;
+}
+
 extern uint8_t __bss_start__;
 extern uint8_t __bss_end__;
 int main(void);
diff --git a/src/card-os.c b/src/card-os.c
index 309c372..49fc59d 100644
--- a/src/card-os.c
+++ b/src/card-os.c
@@ -17,6 +17,10 @@ const uint8_t DISPLAY_CS = 5;
 const uint8_t DISPLAY_DC = 4;
 spi_inst_t* const DISPLAY_SPI = spi0;
 
+const uint8_t BUTTON_LEFT = 15;
+const uint8_t BUTTON_MIDDLE = 16;
+const uint8_t BUTTON_RIGHT = 17;
+
 extern uint8_t __user_ram_start;
 
 typedef int (*user_program_fn)(void);
@@ -24,7 +28,7 @@ static volatile user_program_fn user_program;
 
 void core1_entry(void);
 void os_task(void);
-void os_handle_message(const os_message* msg, os_message* out);
+void os_handle_message(os_message* msg);
 
 int main(void)
 {
@@ -37,6 +41,14 @@ int main(void)
   gpio_set_function(DISPLAY_DC, GPIO_FUNC_SIO);
   gpio_set_dir(DISPLAY_DC, GPIO_OUT);
 
+  gpio_set_dir(BUTTON_LEFT, GPIO_IN);
+  gpio_set_dir(BUTTON_MIDDLE, GPIO_IN);
+  gpio_set_dir(BUTTON_RIGHT, GPIO_IN);
+
+  gpio_pull_up(BUTTON_LEFT);
+  gpio_pull_up(BUTTON_MIDDLE);
+  gpio_pull_up(BUTTON_RIGHT);
+
   spi_init(DISPLAY_SPI, 100 * 1000 * 1000);
   spi_set_format(DISPLAY_SPI, 8, SPI_CPOL_1, SPI_CPHA_1, SPI_MSB_FIRST);
 
@@ -139,13 +151,11 @@ void os_task(void)
     os_message msg = core1_buffer.buffer[index];
     core1_buffer.read_index
       = (core1_buffer.read_index + 1) % OS_RING_BUFFER_SIZE;
-    os_message out;
-    os_handle_message(&msg, &out);
-    out.command = msg.command;
+    os_handle_message(&msg);
     int wrote_index = -1;
     while (wrote_index < 0)
     {
-      wrote_index = os_ring_buffer_write(&core0_buffer, &out);
+      wrote_index = os_ring_buffer_write(&core0_buffer, &msg);
     }
     multicore_fifo_push_blocking(wrote_index);
   }
@@ -155,7 +165,7 @@ extern uint8_t __end__;
 extern uint8_t __StackLimit;
 
 static uint8_t* heap_end;
-void os_sbrk(const ptrdiff_t* incr, void** out)
+void os_sbrk(ptrdiff_t* incr)
 {
   if (!heap_end)
   {
@@ -167,12 +177,12 @@ void os_sbrk(const ptrdiff_t* incr, void** out)
 
   if (next >= &__StackLimit || next < &__end__)
   {
-    *out = (void*)-1;
+    *incr = -1;
   }
   else
   {
     heap_end = next;
-    *out = prev;
+    *incr = (ptrdiff_t)prev;
   }
 }
 
@@ -182,16 +192,39 @@ void os_put_rect(const card_os_rect* rect)
                    rect->h);
 }
 
-void os_handle_message(const os_message* msg, os_message* out)
+void os_get_button(int* button)
+{
+  switch (*button)
+  {
+  case OS_BUTTON_LEFT:
+    *button = !gpio_get(BUTTON_LEFT);
+    break;
+
+  case OS_BUTTON_MIDDLE:
+    *button = !gpio_get(BUTTON_MIDDLE);
+    break;
+
+  case OS_BUTTON_RIGHT:
+    *button = !gpio_get(BUTTON_RIGHT);
+    break;
+  }
+}
+
+void os_handle_message(os_message* msg)
 {
   switch (msg->command)
   {
   case OS_CMD_SBRK:
-    os_sbrk(msg->data, &out->data);
+    os_sbrk(msg->data);
     break;
+
   case OS_CMD_DRAW_RECT:
     os_put_rect(msg->data);
     break;
+
+  case OS_CMD_GET_BUTTON:
+    os_get_button(msg->data);
+    break;
   }
 }